Multimode Base Station

ABSTRACT

A method of controlling admission of a user equipment to a cell of a multi-mode base station, being a base station arranged to operate as a plurality of cells, the plurality of cells comprising at least a first cell and a second cell, and the method comprising: determining information relating to the first cell, and controlling admission of a user equipment to the second cell in dependence on the information relating to the first cell.

1. PRIORITY CLAIM

This application claims priority to and the benefit of Great BritainApplication No. 1105769.2 filed on Apr. 5, 2011.

2. FIELD OF THE INVENTION

The present invention relates to controlling admission of user equipmentto a cell of a multimode base station (such as multimode picocell,femtocell or the like) which is arranged to operate as two or morelogical cells.

3. RELATED ART

As will be familiar to a person skilled in the art, a base station isthe unit which provides a user equipment such as a mobile phone orcomputer with access to a wireless cellular network such as a networkoperating according to both 3G and 4G standards, the base station beingthe first stage up from the user equipment in the cellular hierarchy,i.e. the unit with which the user equipment immediately communicates viaa wireless connection (without an intermediary station). According to3GPP terminology, a base station is sometimes referred to as a “node B”,but the more generic term “base station” will be maintained herein forconvenience.

A femtocell is a type of cellular base station designed to operate overa relatively short range compared to a conventional base station.Short-range dedicated base stations such as femtocells have become moreviable in recent years due to reduction in the cost and size of theelectronics required to implement a cellular base station. The idea isto provide a dedicated base station to cover a relatively smallgeographical area which is expected to experience a high density ofusers and/or regular usage. For example femtocells are typicallyintended to be deployed in a small office, shop, café or even the home.Other types of short range base stations include picocells ormicrocells, typically covering an intermediately sized area; althoughthe scope of femtocells is increasing as they are encroaching on whathave been traditionally called picocells and microcells, supportinglarge offices, shopping malls and outdoor deployments. The scope offemtocells is increasing due to increased functionality over picocellsand microcells. In some wireless standards, femtocells combine thefunctionality of several wireless network elements, for example in UMTSa femtocell combines the functionality of a base station and radionetwork controller (RNC). Also, it is typical for a femtocell to beinstalled by the end user, not the network operator, and extrafunctionality is required to support this, such as the ability to locate(sniff) neighboring base stations. This is in contrast to picocells andmicrocells that are installed by a network operator and only providebase station functionality.

Base-stations (BS), including femtocells, contain a radio resourcemanagement (RRM) entity which includes admission control mechanisms todecide whether a new connection request from a user equipment (UE)should be admitted. This RRM entity may refuse the UE access to the BSdue to it being congested and unable to support more users. Thiscongestion can be on the air-interface, but could also be related tohardware processing resources, or back-haul congestion. When abase-station experiences congestion it has the following options:

-   -   If the UE is very high priority, for example, an emergency call,        it must accept this UE and release or downgrade an alternative        UE.    -   The base-station can direct the UE to an alternative        base-station for service, where this base-station could be at a        different frequency sub-band or a different radio access        technology (RAT).    -   The base-station can offer to service the UE with a lower        quality of service (QOS) than it requested.    -   The base-station can refuse service to the UE and not provide        any alternatives.

A dual-mode femtocell is a base-station operating as two cells. Thesecells could be operating as different RATs, or the same RATs but indifferent sub-bands. Each cell operates an independent RRM admissioncontrol mechanism.

SUMMARY

If both the cells operate an independent RRM admission control mechanismthen this can lead to inefficient use of base-station resources—a UEcould be admitted to the least optimum cell for its QOS, or one cellcould be fully loaded while the other is only lightly loaded.Improvements could be achieved by performing joint admission control fora dual-mode femtocell. These improvements can be related to thethroughput and QOS achieved by the admitted UE, other UE in the samecell, or UEs in neighboring cells.

Therefore according to one aspect of the present invention, there isprovided a method of controlling admission of a user equipment to a cellof a multi-mode base station, being a base station arranged to operateas a plurality of cells, the plurality of cells comprising at least afirst cell and a second cell, and the method comprising: determininginformation relating to the first cell, and controlling admission of auser equipment to the second cell in dependence on the informationrelating to the first cell.

In embodiments the determination of the information may comprisemonitoring statistics of past behavior of the user equipment whenconnected to the first cell, and the control of admission may bedependent on the statistics of the past behavior of the user equipmentin the first cell.

The method may comprise monitoring statistics relating to past behaviorof the user equipment when connected to the second cell, and controllingadmission of the user equipment to the second cell in dependence on thestatistics relating to past behavior of the user equipment in both thefirst cell and the second cell.

The method may comprise receiving a request from the user equipment foradmission to the first cell and, in response to the request foradmission to the first cell, admitting the user equipment to the secondcell based on the statistics relating to past behavior of the userequipment in the first cell.

The admission of the user equipment to the second cell in response tothe request for admission to the first cell may be based on thestatistics relating to past behavior of the user equipment in both thefirst cell and the second cell.

The user equipment may be admitted to the second cell based on thestatistics relating to past behavior before the user equipment indicatesquality of service requirements to the base station.

The method may comprise receiving a request from the user equipment foraccess to the second cell, and in response to the request admitting theuser equipment to the second cell based on the statistics relating topast behavior of the user equipment in the first cell.

The admission of the user equipment to the second cell may be based onthe statistics relating to past behavior of the user equipment in boththe first cell and the second cell.

The user equipment may be admitted to the first cell based on thestatistics relating to past behavior before the user equipment indicatesquality of service requirements to the base station.

The statistics relating to past behavior of the user equipment maycomprise at least one of: a downlink throughput requested by the userequipment from the respective cell, and an uplink throughput requestedby the user equipment from the respective cell.

The statistics relating to past behavior of the user equipment maycomprise at least one of a downlink throughput used by the userequipment in the respective cell, and an uplink throughput used by theuser equipment in the respective cell.

The statistics relating to past behavior of the user equipment maycomprise at least one of a downlink latency requested by the userequipment from the respective cell, and an uplink latency requested bythe user equipment from the respective cell.

The statistics may represent a predetermined period, the method maycomprise determining an average of the statistics representing theperiod, and the control of admission may be based on the average.

The method may comprise determining a variation of the average of thestatistics representing the period, and the control of admission may bebased on the variation of the average. The statistics may represent apredetermined period of at least one day. The statistics may represent apredetermined period of at least one week. In further embodiments, thedetermination of the information may comprise determining a predictionof performance of the first cell, and the control of admission may bedependent on the prediction of performance in the first cell.

The method may comprise determining a prediction of performance of thesecond cell, and the control of admission may be dependent on theprediction of performance for both the first cell and the second cell.

The method may comprise receiving a request from the user equipment foradmission to the first cell; and, in response to the request foradmission to the first cell, admitting the user equipment to the secondcell based on the prediction of performance of the first cell.

The admission of the user equipment to the second cell in response tothe request for admission to the first cell may be based on theprediction of performance of both the first cell and the second cell.

The user equipment may be admitted to the second cell in response to therequest for admission to the first cell without being admitted to thefirst cell between the request for admission to the first cell and theadmission to the second cell.

The method may comprise receiving a request from the user equipment foraccess to the second cell, and in response to the request admitting theuser equipment to the second cell based on the statistics relating topast behavior of the user equipment in the first cell.

The admission of the user equipment to the second cell may be based onthe prediction of performance of both the first cell and the secondcell. The determination of performance may comprise a measure of atleast one of: downlink throughput, downlink latency, uplink throughput,and uplink latency.

The measure may comprise at least one of: a maximum downlink throughputof the respective cell, a minimum downlink latency of the respectivecell, a maximum uplink throughput of the respective cell, and a minimumuplink latency of the respective cell.

The measure may comprise a measure of an available air interfaceresource of the respective cell. The measure may comprise a measure of ahardware resource of the base station available for the respective cell.The measure may comprise a measure of path loss for the respective cell.The measure may comprise a power limit of the respective cell. Themeasure may comprise an estimate of noise and/or interference in therespective cell. In yet further embodiments, the control of admissionmay be based on comparison of the past behavior with the predictedperformance.

According to another aspect of the present invention, there is provideda multi-mode base station arranged to operate as a plurality of cells,the plurality of cells comprising at least a first cell and a secondcell, and the base station comprising a radio resource manager forcontrolling admission of a user equipment to the cells, the radioresource manager being configured to perform operations in accordancewith any of the above combinations of method features.

According to another aspect of the present invention, there is provideda computer program product for controlling access to a cell of amulti-mode base station, being a base station arranged to operate as aplurality of cells, the plurality of cells comprising at least a firstcell and a second cell, and the computer program product being embodiedon a non-transient computer-readable medium and configured so as whenexecuted on a processor of the base station to perform the operations ofany of the above combinations of method features.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how itmay be put into effect, reference is made by way of example to theaccompanying drawings in which:

FIG. 1 is an illustration of a part of a wireless cellular communicationnetwork, and

FIG. 2 is a flow chart of a method of controlling access to a multi-modebase station.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram showing a part of a wireless cellularcommunication network such as a 3G network. The network comprises a userequipment (UE) 2 in the form of a mobile terminal, such as a smart phoneor other mobile phone, a tablet, or a laptop or desktop computerequipped with a wireless data card. The network further comprises a basestation in the form of a femtocell 4, and one or more further basestations 6. Each base station 4, 6 provides network coverage in the formof at least one respective cell 4 a, 4 b, 6 a.

Furthermore, the femtocell 4 is configured as a dual mode femtocell. Adual-mode femtocell is a base station operating as two logical cells 4 aand 4 b. These cells 4 a, 4 b may be configured to operate according todifferent radio access technologies (RATs), i.e. differenttelecommunication standards. For example one of the dual cells may bearranged to operate according to a 3G standard such as a UniversalMobile Telecommunications System (UMTS) standard and the other of thedual cells may be arranged to operate according to a 4G standard such asa Long Term Evolution (LTE) standard. Alternatively, the cells 4 a, 4 bmay be arranged to operate according to the same RAT but in differentfrequency sub-bands. The reach of the cells 4 a, 4 b does notnecessarily extend across exactly the same geographical area. Range ishighly dependent on RAT and frequency, e.g. cell 4 a could be twice thesize of cell 4 b. The arrangement shown in FIG. 1 is only schematic. Ona point of terminology, note that “base station” or “femtocell” refersto the unit, whilst “cell” refers to the logical combination ofgeographical coverage area and access technology or frequency band (alsonote that in the context of the present application “femtocell” refersto the base station unit rather than the cell). As the two cells 4 a, 4b are provided by the same base station unit then they share the samecell center point, i.e. represent the same geographical node of thenetwork, and they also share at least some of the same hardwareresources. For example a dual-mode base station 4 typically shares thesame processor for both cells 4 a, 4 b, though typically not the sameantenna. The dual cells 4 a, 4 b typically also share other base-stationfunctionality, such as configuration management, synchronization andbackhaul connection (i.e. same connection to the next element up in thecellular hierarchy).

The invention could apply equally to any multi-mode base station, but byway of illustration the following embodiments are described in relationto a dual-mode femtocell 4.

The user equipment 2 is arranged to be able to request admission to aparticular cell, and when it does so, e.g. requesting admission to cell4 a, to request a particular quality of service. For example it couldrequest to be provided with at least a certain uplink or downlinkthroughput, or to be provided with no more than a certain uplink ordownlink latency.

Each of the base stations comprises a radio resource manager (RRM)arranged to receive the admission request from the UE and decide whetherto admit the user equipment 2 to the requested cell. Conventionally thisis done in the manner described in the background section above by anindependent RRM for each cell 4 a, 4 b, 6 respectively, includingindependent admission control for each of the dual cells 4 a, 4 b.However, according to the present invention there is provided a jointadmission control mechanism which shares information between the two ormore cells 4 a, 4 b of a multimode base station such as a dual-modefemtocell 4, i.e. shares information relevant to service quality in thetwo or more cells. This allows the radio resource manager for arequested cell 4 a to make a decision not only based on information ofthe requested cell 4 a itself, but also based on information of the oneor more alternative other cells 4 b of the multimode base station 4.

At a higher level of the cellular hierarchy the network may comprise oneor more higher-level controller stations, which may be arranged toperform various further management functions. However, the presentinvention is concerned with radio resource management at the level of amulti-mode base station.

According to a first embodiment of the present invention, the process ofdetermining the throughput and/or other QOS requirements of a UE 2 canbe enhanced by storing long-term statistics of UE behavior at the RRM.This allows the RRM to use past-behavior to admit the UE to the mostappropriate cell 4 a, 4 b of a dual-mode femtocell 4.

The joint RRM can keep a history of the past connections for a specificUE 2, and this can be used to determine the services and throughputrequirements that a specific UE typically uses. The long-term parameterskept by the RRM can include the following:

-   -   Requested downlink throughput    -   Requested uplink throughput    -   Utilized downlink throughput    -   Utilized uplink throughput    -   Requested downlink latency    -   Requested uplink latency

For these parameters, one or more of the following statistics can becollected:

-   -   Long-term average values for the parameters, giving a measure        for basic prediction    -   Variation for the average over 24 hour periods, to find behavior        patterns across each day.    -   Variation for the average over 7 days, to find behavior patterns        across each week.    -   Short-term average values (over a few hours) to find local        trends.

These parameters and statistics allow the RRM to predict the throughputand/or other QOS requirements of a particular UE 2. The RRM can thendecide whether to continue admitting the UE 2 to the cell 4 a it isrequesting, or whether to immediately admit the UE 2 to an alternative,more appropriate cell 4 b. The use of joint RRM combined with long-termstatistics enables the best cell selection to happen faster, preferablybefore the UE 2 indicates its QOS requirements to the femtocell 4. Inaddition, moving the UE 2 between cells 4 a, 4 b at the start of theadmission process requires fewer signaling messages, thus reducing thesignaling load on the network.

A base station 4 may be configured to operate in one of a plurality ofdifferent available modes. Closed access mode is where the cell onlyprovides a service to a subset of UE which are all members of its closedsubscriber group (CSG). Open access mode is where the cell provides aservice to any UE that are entitled to a service from the networkoperator (i.e. this is identical mode used in macro, micro and picocells today). Hybrid access mode is where the cell provides a service toany UE that are entitled to a service from the network operator, but italso has a list of UE in its CSG. This allows the cell to provide animproved service level to these CSG (if it wants to).

Tracking UE parameters and statistics is most beneficial in a femtocell4 operating in either closed or hybrid mode where a finite closed groupof subscribers exist, which are expected to regularly access thefemtocell. This regular access allows reliable predictions to be made.

The long-term prediction of statistics described above can be eitherused standalone, or used to produce downlink throughput and latencyvalues (Thpt_DL_Req, Latency_DL_Req) and uplink throughput and latencyvalues (Thpt_UL_Req, Latency_UL_Req) to be combined with a secondembodiment of the invention, described below.

According to a second embodiment of the present invention, the selectionof the best cell 4 a, 4 b of the dual mode femtocell 4 can be enhancedby predicting the throughput and latency of each cell that can beachieved.

The downlink throughput and latency which is achievable can bedetermined from:

-   -   The static properties of the cell, for example, minimum        achievable latency and maximum achievable throughput.    -   The available air interface resources based on the number of        currently serviced UEs. For example, in LTE this would be the        number of resource blocks (RB), while for UMTS this would be the        number of codes available.    -   The available hardware resources for the cell which relate to        the total number of UEs supported, or the number of UEs        supported each subframe (LTE) or TTI (UMTS).    -   The pathloss to the UE for this cell, which can be very        different for each cell.    -   Any power limit applied to the cell to protect neighbors in the        same frequency sub-band. This could be determined by pathloss to        neighbors, downlink loading information for the victim BS,        proximity information for the victim UE, and the operating mode        for the femtocell (closed, hybrid, open).    -   Estimation, via sniffing, of the noise and interference floor at        the UE for this frequency sub-band.

Similarly, the uplink throughput and latency which is achievable can bedetermined from:

-   -   The static properties of the cell, for example, minimum        achievable latency and maximum achievable throughput.    -   The available air interface resources based on the number of        currently serviced UEs. For example, in LTE this would be the        number of resource blocks (RB), while for UMTS this would be the        number of codes available.    -   The available hardware resources for the cell which relate to        the total number of UEs supported, or the number of UEs        supported each subframe (LTE) or TTI (UMTS).    -   The pathloss to the femtocell for this cell, which can be very        different for each cell.    -   Any power limit applied to the cell to protect neighbors in the        same frequency sub-band. This could be determined by pathloss to        neighbors and uplink loading information for the victim BS.    -   Estimated of the noise and interference floor at the femtocell        for this frequency sub-band.

These parameters can be used to determine a set of uplink and downlinkthroughput and latency prediction for each cell, denoted by (Thpt_DL_A,Thpt_DL_B, Latency_DL_A, Latency_DL_B) and (Thpt_UL_A, Thpt_UL_B,Latency_UL_A, Latency_UL_B).

The UE is assigned to the cell with the throughput and latencycapabilities which most closely match the UE requirements.

This prediction of achievable throughput and latency is applicable to afemtocell operating in any of the three modes: closed, hybrid or open.

This can be used standalone when the UE reports its QOS requirements tothe base-station, or combined with the UE throughput and QOS predictiondescribed in the first embodiment.

In addition, if a cell is heavily loaded (congested), the first andsecond embodiments of the invention can be used together to form aprediction of throughput and latency of each of multiple UEs, in eachcell. Thus the UE is able to be optimally redistributed at the dual-modefemtocell. For example, the following values would be determined:

-   -   UE1 in RATA, UE2 in RAT A    -   UE1 in RATA, UE2 in RATB    -   UE1 in RATB, UE1 in RATA    -   UE1 in RATB, UE1 in RATB        The most efficient combination of UE and RAT can then be        selected.

The flow chart of FIG. 2 illustrates an example of a preferred decisionmaking process which may be implemented in a joint RRM of a multimodebase station such as a dual mode femtocell 4. The process is preferablyimplemented in the form of computer program code stored on anon-volatile storage medium of the base station 4 (e.g. magnetic memorydevice such as a hard drive or an electronic memory device such as aflash memory) and arranged for execution on a processing apparatus ofthe base station (e.g. single or multi core CPU). However, animplementation involving dedicated hardware is not excluded.

At step S10 the RRM of the femtocell 4 receives a request from the UE 2for admission to a particular cell of the dual mode femtocell 4, e.g.cell 4 a.

At step S20, the RRM consults the past statistics it has accumulated forthe UE 2 when it was connected in the alternative cell 4 b (andpreferably also the past statistics it has accumulated for the UE 2 whenit was connected in the requested cell 4 a itself). Generally the paststatistics can be collected from either cell or both cells. The RRM usesthese statistics to produce expected downlink throughput and/or latencyvalues (Thpt_DL_Req, Latency_DL_Req), and/or to produce uplinkthroughput and/or latency values (Thpt_UL_Req, Latency_UL_Req). Forreasons discussed above, in a particularly preferred implementation thisis done before the UE 2 signals its own requested QOS requirement(s) tothe femtocell 4. The values may be calculated from the statistics inresponse to the request, or for faster response time may be maintainedin advance of the request.

At Step S30, the RRM consults its prediction of performance of thealternative cell 4 b (and preferably also its prediction of performanceof the requested cell 4 a), i.e. its prediction of one or more a prioriproperties that are a feature of the cell itself rather than an aposteriori observed behavior of the UE 2 when connected in the cell.Generally the performance can be determined for either cell or bothcells This results in a set of uplink and/or downlink throughput and/orlatency prediction values for each cell, (Thpt_DL_A, Thpt_DL_B,Latency_DL_A, Latency_DL_B) and (Thpt_UL_A, Thpt_UL_B, Latency_UL_A,Latency_UL_B). Again in a particularly preferred implementation this isdone before the UE 2 signals its own requested QOS requirement(s) to thefemtocell 4; and the values may be calculated from the statistics inresponse to the request, or for faster response time may be maintainedin advance of the request.

At Step S40, the RRM compares the expected QOS requirement(s) of the UE2(Thpt_DL_Req, Latency_DL_Req, Thpt_UL_Req, and/or Latency_UL_Req) withthe predicted performance value(s) of the alternative cell 4 b(Thpt_DL_A, Thpt_DL_B, Latency_DL_A, Latency_DL_B, Thpt_UL_A, Thpt_UL_B,Latency_UL_A, and/or Latency_UL_B), and at step S50 determines based onthe comparison whether the UE 2 should be served by the alternativecell. Preferably this involves also comparing the expected QOSrequirement(s) of the UE2 with the predicted performance value(s) of therequested cell 4 b, and determining whether the requested cell 4 a orthe alternative cell 4 b represents the best match to the UE's needs.

If the RRM decides the UE 2 would not be better served by thealternative cell 4 b, it proceeds to step S60 where it admits the UE 2to the requested cell 4 a. If on the other hand the RRM decides the UEwould be better served by the alternative cell 4 b, it proceeds to stepS70 where it admits the UE 2 to the alternative cell 4 b. This mayinvolve instructing the UE 2 to connect to the alternative cell 4 b oroffering it the option of connecting to the alternative cell 4 b (the UE2 could attempt a connection to a cell 6 a of a different base station 6in response to the offer).

In further embodiments, the RRM may receive requests from multiple UEs 2and may take into account the expected QOS requirements and/or requestedQOS for the multiple UEs, so as to determine an optimal set of decisionsbalancing the needs of all parties involved. The decision making processmay also involve more than two cells of a multimode femtocell or othersuch multimode base station, e.g. by performing multiple instances ofthe above-described comparison process for multiple alternative cellsand determining which comparison results in the best match.

It will be appreciated that the above embodiments have been describedonly by way of example.

For instance, the above has been described in terms of throughput and/orlatency, but other information relevant to service quality could also beused in addition or as an alternative to these, e.g. error rate, loss orjitter.

Whilst it is preferred that the first and second embodiments are usedtogether, this is not necessarily the case. For example the firstembodiment could be used alone by taking the UE's past experience ofhigh throughput or low latency in an alternative one of the multiplecells 4 b as a trigger to admit the UE to that cell 4 b instead of therequested cell 4 a. Or in another example the second embodiment could beused alone by comparing the predicted performance of the alternativecell 4 b with the UE's actual requested QOS, instead of basing thecomparison on the US's expected QOS as would be determined fromstatistics of past behavior according to the first embodiment.

Other variations may become apparent to a person skilled in the artgiven the disclosure herein. The scope of the invention is not limitedby the described embodiments but only by the claims.

1. A method of controlling admission of a user equipment to a cell of amulti-mode base station, being a base station arranged to operate as aplurality of cells, the plurality of cells comprising at least a firstcell and a second cell, and the method comprising: determininginformation relating to the first cell, and controlling admission of auser equipment to the second cell in dependence on the informationrelating to the first cell.
 2. The method of claim 1, wherein: thedetermination of the information comprises monitoring statistics of pastbehavior of the user equipment when connected to the first cell, and thecontrolling admission is dependent on the statistics of the pastbehavior of the user equipment in the first cell.
 3. The method of claim2, comprising monitoring statistics relating to past behavior of theuser equipment when connected to the second cell, and controllingadmission of the user equipment to the second cell in dependence on thestatistics relating to past behavior of the user equipment in both thefirst cell and the second cell.
 4. The method of claim 2, furthercomprising receiving a request from the user equipment for admission tothe first cell and, in response to the request for admission to thefirst cell, admitting the user equipment to the second cell based on thestatistics relating to past behavior of the user equipment in the firstcell.
 5. The method of claim 3, wherein the admission of the userequipment to the second cell in response to the request for admission tothe first cell is based on the statistics relating to past behavior ofthe user equipment in both the first cell and the second cell.
 6. Themethod of claim 4, wherein the user equipment is admitted to the secondcell based on the statistics relating to past behavior before the userequipment indicates quality of service requirements to the base station.7. The method of claim 2, further comprising receiving a request fromthe user equipment for access to the second cell, and in response to therequest admitting the user equipment to the second cell based on thestatistics relating to past behavior of the user equipment in the firstcell.
 8. The method of claim 3, wherein the admission of the userequipment to the second cell is based on the statistics relating to pastbehavior of the user equipment in both the first cell and the secondcell.
 9. The method of claim 7, wherein the user equipment is admittedto the first cell based on the statistics relating to past behaviorbefore the user equipment indicates quality of service requirements tothe base station.
 10. The method of claim 2, wherein the statisticsrelating to past behavior of the user equipment comprise at least one ofa downlink throughput requested by the user equipment from therespective cell, and an uplink throughput requested by the userequipment from the respective cell.
 11. The method of claim 2, whereinthe statistics relating to past behavior of the user equipment compriseat least one of a downlink throughput used by the user equipment in therespective cell, and an uplink throughput used by the user equipment inthe respective cell.
 12. The method of claim 2, wherein the statisticsrelating to past behavior of the user equipment comprise at least one ofa downlink latency requested by the user equipment from the respectivecell, and an uplink latency requested by the user equipment from therespective cell.
 13. The method of claim 2, wherein the statisticsrepresent a predetermined period, and the method further comprisesdetermining an average of the statistics representing the period, andthe control of admission is based on the average.
 14. The method ofclaim 13, further comprising determining a variation of the average ofthe statistics representing the period, and the control of admission isbased on the variation of the average.
 15. The method of claim 1,wherein: the determination of the information comprises determining aprediction of performance of the first cell, and the control ofadmission is dependent on the prediction of performance in the firstcell.
 16. The method of claim 15, further comprising determining aprediction of performance of the second cell and the control ofadmission is dependent on the prediction of performance for both thefirst cell and the second cell.
 17. The method of claim 15, furthercomprising receiving a request from the user equipment for admission tothe first cell and, in response to the request for admission to thefirst cell, admitting the user equipment to the second cell based on theprediction of performance of the first cell.
 18. The method of claim 17,wherein the admission of the user equipment to the second cell inresponse to the request for admission to the first cell is based on theprediction of performance of both the first cell and the second cell.19. A multi-mode base station arranged to operate as a plurality ofcells, the plurality of cells comprising at least a first cell and asecond cell, and the base station comprising: a radio resource managerfor controlling admission of a user equipment to the cells, the radioresource manager being configured to: determine information relating tothe first cell, and control admission of a user equipment to the secondcell based on the information relating to the first cell.
 20. A computerprogram product for controlling access to a cell of a multi-mode basestation, the a base station arranged to operate as a plurality of cells,the plurality of cells comprising at least a first cell and a secondcell, and the computer program product being embodied on a non-transientcomputer-readable medium and configured such that when executed on aprocessor of the base station it determines information relating to thefirst cell, and controls admission of a user equipment to the secondcell based on the information relating to the first cell.